Various mechanisms exist for formatting and compressing binary code images for storing in a storage device. In this context, a binary code image is typically an executable image, or any image that is executed, for example on a personal computer (PC), or in firmware, etc., or on any processing system where a computer program is used to accomplish some task. Any image that is to be executed on a processor must have a standard format so that the target processor firmware can recognize that the image may be executed from flash memory, or loaded into memory or executed in another manner. A common standard used in existing PC systems to be used for executable images is the portable executable, common object file format (PE/COFF) specification, entitled, Microsoft Portable Executable and Common Object File Format Specification, Revision 6.0, Microsoft Corporation, February 1999, and may be found on the World Wide Web at http://www.microsoft.com/whdc/hwdev/hardware/PECOFF.mspx. This format is portable because the formatted file is meant to be executed on different targets. For instance a PE/COFF image might be executed in both a WIN/CE environment, as well as, a Windows® XP environment. As long as the target processor recognizes a PE/COFF format, the processor can execute the PE/COFF formatted image.
To execute on different platforms, the PE/COFF image must contain specific information related to possible target platform and operating systems. Thus, there may be information in the PE/COFF image that is not relevant to every possible target platform. Not all fields will be applicable to all platforms.
For instance, the PE/COFF image may be a device driver. The device driver may reside in flash memory. It is desirable to reduce the size of the device driver in flash memory to save valuable space on this storage device. In existing systems, space saving techniques are often limited to compression of the image content. In some cases, the entire image file, including headers is compressed.
A device driver image is typically developed to be available on multiple computing platforms. Having one executable reduces configuration and development/maintenance costs for the vendor. The header of the image may indicate that different modules or routines are applicable for different platforms, perhaps by including a pointer or virtual address. Some executables must be executed from a real address in flash memory. These executables are called XIP (eXecute In Place), and cannot be relocated, for example. Other executables may be relocated to memory. This information may be included in the PE/COFF image itself.
In existing systems, a PE/COFF image is delivered to multiple platforms and loaded into flash memory on the target platform. If the image is of the type XIP, the image cannot be compressed on the flash memory, because the image must be executed from the flash memory. Therefore, the information residing on the flash memory must be directly executable instructions. Other images may be compressed before loading into flash memory. There are a variety of methods known in the art to compress executable images before writing to a flash memory.